Triazole-Bridged Zinc Dinuclear Complexes: Mechanochemical Synthesis, Crystal Structure, and Biological Activity.

Two zinc (Zn) complexes, [Zn(DAT)Cl] () and [Zn(DAT)(NO)] (), were prepared by grinding 3,5-diamino-1,2,4-triazole (CHN, DAT) with Zn precursors such as ZnCl and Zn(NO), respectively. This solid-state reaction gives the corresponding Zn complex as the sole product in over 99% yield. This mechanochemical method promotes the selective formation of Zn complexes different from those obtained using the conventional solution-based route. The crystal structures of the two complexes were analyzed by single-crystal X-ray diffraction. Complex () crystallizes in the monoclinic space group 2/, whereas complex () crystallizes in the triclinic space group . Each complex is characterized by the presence of a characteristic DAT-bridged dimer with one DAT ligand per Zn atom, and the DAT ligand provides a bridge between the two Zn metals. All Zn centers of () and () adopted a slightly distorted tetrahedral geometry. Both complexes contain a hexanuclear ZnN ring, but their ring structures are different. Complex () possesses a boat geometry, while complex () has a nearly planar structure. The Zn-bound chlorides of complex () form intermolecular N-H···Cl hydrogen bonds that link neighboring molecules. In complex (), the O atoms in the nitrate groups are hydrogen-bonded to the DAT ligand via O···H-N linkages. Both complexes exhibit blue emissions in the solid state at ambient temperature. They were evaluated as anticancer agents in HeLa, NCCIT, and MCF-7 cancer cell lines, exhibiting promising anticancer activities.